Process of treating photographic prints.



5 mto single points or dots takes place, which UNITED srngns n'rnnr nron.

TO THE FIRM OF KLIMSOH & CO.,

MANY.

OF FRANKFORT-ON-THE-MAIN, GER- PROCESS OF TREATING PHOTOGRAPHIC PRINTS.

Specification of Letters Patent.

Patented March 12, 1907.

Application filed December 27. 1905. Serial No. 293,532-

1'2) all whom it may concern.-

Be it known that I, PETER SOHUMAOHER, doctor of philosophy, chemist, 'a subject of the German Emperor, and a resident of No. 129 Griineburgweg, Frankfort-on-the-Main, Kingdom of Prussia, German Empire, have invented new and useful Improvements in the Process ofTreating Photographic Prints, of which the following is a specification.

The operation of decomposing a photographic copy into a system of grains or dots .in the art of reproduction generally is made either optically by placing before the sensitired plate a lined or grained screen or mechanically by printing on grained surfaces. To obtain a grain chemically has hitherto only been possible in collotype or collotype transfer, in which process the grain is formed by the exposed coating itself. In the new invention the exposed coating takes also part in the formation of the grain, the new processbeing due to the discovery that by volat-ilizing a solution of resins, balsams, oils, greases, and so on upon an exposed sensitized plate a precipitation of the resin and so on correspond in size and disposition to the tints and the design of the picture. If, for instance, a half-tone negative is copied upon a. coating of chromatic alum, volatilizing upon a plate a solution of powdered resin of two to three per cent. in absolute alcohol, the resin will be found precipitated as a system of dots sticking firmly on the plate and forming a perfect decomposition of the tints of the picture, with all its peculiarities and fineness. In order to obtain an especially uniform secretion of the grain,the flooding of the plate and the volatilizing of the resinous solution can be made on a Whirler the. quickness of which can be regulated. The arrangement of the dots differs from that produced by the processes hitherto known by the fact that the dots do not cover the surface equally without reference to the design, but that they attach themselves along the lines of the design and have an arrangement correspondent to the lines in the direction of their grouping.

The chief conditions for carrying out the process are as follows: constant temperature of the copied plate, of the resinous solu- .tion, and the room wherein the secretion of the grain is made, besides a constant degree of dampness of the latter. All these condi tions must be attended to very closely in order to obtain a complete breaking up of the picture and constant results. It is of the utmost importance to keep up a fixed degree of dampness, and in order to obtain this with all certitude in the face of the ever-oscillating atmospheric dampness the secretion of the grain must be carried out in'a box separated rom the atmosphere, the capacity of dampness of which is maintained constant by passing through it a current of air dried or damped before or by other proper mediums. Asit is very difficult, however,

j even with the expedients mentioned above, to obtain a fixed degree of dampness, owing to the variation of the dampness of the air, the only especially practical medium left is working in a room completely or nearly completely saturated with dampness. This condition can be filled very easlly and withabsolute certitude by suspending wet clothes, by sprinkling water inside the box, by introducing a current before with water by passing through some washing tubs filled with Water, provided that the temperature of the box he kept at a fixed height, the absolute and relative degree of dampness will remain perfectly constant, and there have been created the uniform main conditions which are absolutely necessary without being dependent upon the atmosphere.

As a matter of course there cannot be produced a proper grain under ordinary circumstances in so high a dampness, and it is necessary, therefore, to heat the plate before, and perhaps also its bed, so that the temperature of same may exceed that of the room in which the secretionof the' grain is made. In this case it is advisable to heat also the resinous solution before in order to avoid a cooling of the plate when the plate is flooded.

of air which has been saturated The measurements of the box must be '7 ries of conditions-such as, for instance, the t degree of exposure, the quality and quantity of the resin, the quickness of the evaporation, and so on. It is obvious.v that this changes the character and'the arrangements of the dots, so that it is of utmost importance to keep up alwaysthe same conditions.

The resin eliminated sticks firmly to the plate, which thencan be etched and prepared for any of the different methods 'of printing. To sensitize the plates, there can and with or Without greases, oils, and so on.

These substances according to the circum-' stances can be used pure or mixed. A rs dis.- solving mediums can be used according to circumstances the different 11 qulds WhlCll are suitable to the above-mentioned substances.

Instead of the merely alcoholic solution of the resin there can be used successfully also a mixture of petrolic ether and alcohol; yet it is advisable to subject the former to the fractionate distillation and use always the same fractions. It may be mentioned that nearly all the ingredients added to the sensitized coating or to the resinous solution have a certain influence on the formation, even then if the addedbodies can be considered as neutral ones or of little effect. It is impossible, therefore, to enumerate'here all the ingredients which may be added and What may be the effect theycall forth on the sensitized late. Special attention is called only to the ollowing points:. Calcium chlorid added to the resinous solution produces a round shape andlarge number of the eliminated dots 111 the light parts. cording to the quantity a close shading in the formation of the grain and a round grain in the light parts.

Alkalies, especially ammoniac, cause abetter adaptation of the grain to the tints, of the copy. An increase of the concentration of the resinous solution gives a coarser grain, which can be obtained also by reducing the rapidity ofthe whirler" upon which the plate is placed during the evaporation of the resin ous solution.- It is obvious, therefore, that by means of varying the concentration of the 1 solution of the ingredients and the rapidity the operator is in a position of obtaining Turpentine calls forth acevery finenessof grain desired. The process is appropriate'for every method of printing and of special advantage-to color-printing,

owing to the fact that the grain is not. ar-

ranged according'to a certain system of lines and every production of Moir is entirely 1. The process for decomposing photographic pictures into a system of grams by evaporating on a sensitized plate a resinous solution-in suitable solvents.

2. The process for decomposing photographic pictures into a system of grains by evaporating on a sensitized plate a resinous solution in suitable solvents, characterized by the fact that the evaporation is carried out under the same conditions of heating and dampness of the plate, of the resinous solution andv the laboratory respectively;

3. The. process for decomposing photographic pictures into a system of grains by evaporating on a sensitized plate a resinous solution in suitable solvents characterized by the addition of ingredients such as other resinoids or calcium chlorid, tu. entine or alkalies for producing the modi cation of the grain by variation of the concentration of the solution.

4. The process for decomposing photographic pictures into a system of grains by evaporating on a sensitized plate a resinous solution in suitable solvents in which the production of the grain is efiected 'in a room separated from the atmos here the dampness of which is maintaine constant by appropriate mediums.

5. The process for decomposing graphic pictures into a system of grains by evaporating on a sensitized plate a'resinous solution in suitable solvents in which the production "of the grain is effected in a room nearly or completely saturated with dampness, the plate and its bed being-previous y heated and in which calcium chlorid and phototurpentine are added to the resinous'solution.

' In testimonythat I claim the foregoing as my invention I have signed my name. in presence of two witnesses, this 13th day of December, 1905.

' PETER SCHUMACHER;

V Witnesses:

EVA SATTLER, OSKAR STANDHARDT. 

